U.S. Pat. Nos. 4,751,319; 4,812,501 and 4,831,178 describe aliphatic and aryl esters of 1,3,2-oxazaphospholidines as color improvers and process stabilizers for various polymer substrates. The compounds described in these patents are all substituted on the 3-N atom of the 1,3,2-oxazaphospholidine moiety by a tert-alkyl moiety. The instant compounds are both structurally distinguished thereover and superior in stabilizing properties.
The instant compounds are not only distinguished from the prior art compounds structurally, but they exhibit surprising stabilizing properties which further distinguish them from the prior art. This is manifested in the superior processing stabilization of polymeric substrates in terms of melt flow stabilization and resistance to discoloration. When R.sub.1 and R.sub.2 are both alkyl (e.g. methyl), the instant compound exhibits improved hydrolytic stability because of the gem-dialkyl groups.